A negative end-expiratory transpulmonary pressure indicates what?

A negative end-expiratory transpulmonary pressure indicates what?

• A. Overdistension
• B. Net collapsing pressure on the lungs
• C. High airway resistance
• D. Increased chest wall compliance

Answer: (B)

End-expiratory transpulmonary pressure is the distending pressure across the lung at the end of expiration, calculated as airway pressure minus pleural pressure. When this value is negative, it means pleural pressure is higher than airway pressure at end expiration. That creates a net collapsing pressure on the lungs, so the lung tends to recoil inward rather than stay open. In other words, the forces driving collapse dominate at end expiration unless countered by something like PEEP. Overdistension would require a positive transpulmonary pressure, not a negative one. High airway resistance affects airflow rather than the static pressure balance at the end of expiration. Increased chest wall compliance changes how the chest wall and lung balance but does not by itself mandate a negative end-expiratory transpulmonary pressure.

End-expiratory transpulmonary pressure is the distending pressure across the lung at the end of expiration, calculated as airway pressure minus pleural pressure. When this value is negative, it means pleural pressure is higher than airway pressure at end expiration. That creates a net collapsing pressure on the lungs, so the lung tends to recoil inward rather than stay open. In other words, the forces driving collapse dominate at end expiration unless countered by something like PEEP.

Overdistension would require a positive transpulmonary pressure, not a negative one. High airway resistance affects airflow rather than the static pressure balance at the end of expiration. Increased chest wall compliance changes how the chest wall and lung balance but does not by itself mandate a negative end-expiratory transpulmonary pressure.